Using hydrogen doesn't emit carbon. But the principal way hydrogen is produced is called steam reformation. It's a process that turns methane (CH4) and water (2* H2O) into hydrogen (4* H2) and CO2 (i think, I'm not an expert). So all the carbon get emitted as co2. So it's not better, and there are a bunch of inefficiencies too. (The reformation process itself, and transportation challenges, and leakage). But theoretically, it does centralize the emissions which would make them easier to sequester so there's that.

In the USA for example about 99% of commercial Hydrogen is a byproduct of Steam Cracking Petroleum refinement. We have the technology to create hydrogen via other methods, but so far we're not really utilizing them. Still, as a byproduct it's better to use it than to not.

it's the production of the hydrogen that's done improperly. Similar to how electricity doesn't cause emissions, but coal power plants do